1. Field of the Invention
The present invention relates to an improved operation mechanism of a height adjusting device or height adjuster (a vertically adjusting mechanism) which is capable of adjusting independently the heights of the front and rear portions of a seat cushion (a sitting part of a seat) in an automotive seat.
2. Description of the Prior Art
In a type of a conventional height adjusting device which is adapted to raise or lower the front and rear portions of a seat cushion of an automotive seat independent of each other, an operation knob is located in the front portion of the seat, which results in a very poor operationability. Also, in another type of such conventional height adjusting device, although the operation knob is disposed on the side surface of the seat cushion, because the range of adjustment of height thereof is previously set stepwise, the height of the seat cannot be adjusted to an occupant's taste in a sufficient manner.
In order to avoid the above-mentioned disadvantages, there is proposed still another type of height adjusting device (for example, Japanese Utility Model Publication No. 16622 of 1985), as shown in FIG. 1, wherein a lower arm (102) of a reclining adjuster is located on the side surface of a seat cushion (101), two rotary shafts (103), (104) are mounted onto the arm (102) such that they intersect the arm (102) at right angles, rotary members, that is, sector gears (105), (106) intermeshable with pinion gears (112), (113) in the rotary shafts (103), (104) are rotatably mounted to an upper rail of a seat adjuster respectively, one rotary member (105) is connected via a link (107) to the front portion of a seat cushion frame, the other rotary member (106) is connected to the rear portion of the seat cushion frame via a connecting rod (108) and a link (109), and two operation knobs (110), (111) are attached to the rotary members (105), (106), respectively.
However, according to the above-mentioned conventional height adjuster operation mechanism, as shown in FIG. 2 which is a perspective view thereof, due to the fact that two kinds of operation knobs (110), (111) respectively adapted to raise and lower the front and rear portions of the seat cushion independent of each other are disposed mutually in front and in rear of each other on the side surface of the seat cushion, they must be spaced apart from each other so as to avoid their wrong use, with the result that the front operation knob (110) is too far from the reach of an occupant and the rear operation (111) may often be abutted against the bottom through the thigh portion of the occupant when the occupant gets into or out of an automobile, impairing the sitting feeling of the occupant. Also, in view of space, the design of the operation mechanism is limited, which provides another drawback.